Process for uniformly coating printing supports



Sept. 23, 1941. R. KAULEN PROCESS FOR UNIFORMLY COATING PRINTING SUPPORTS 2 Sheets-Sheet 1 Filed June 5, 1957 [80M [flue/772w 77pm M Affomeus Sept. 23, 1941. R. KAULEN' 2,256,777- PROCESS FOR UNIFORMLY COATING PBINTING SUPBORTS Filed June 5, 1957 v2 Sheets-Sheet 2 [nu enzor heated container.

Patented Sept. 23, 1941 PROCESS FOR UNIFORM'LY COATING PRINTING SUPPORTS Robert Kaulen, Loevenich, near Cologne-on-the Rhine,

Germany, assignor to the firm Eden A. G., Zug, Zurich, Switzerland Applicatig: June 3, 1937, Serial No. 146,228

Germany June 5, 1936 1 Claim.

' and uniformly coated with the light sensitive layer, it is of the utmost importance that the'printingsupport, such as the metal cylinder, must be kept just at such a temperature before and during the light sensitive colloidal liquid or emulsion is applied thereon, that the viscosity of this fluid or emulsion duringits application does not undergo any change resulting in a lack of homogeneity of the coating. For this purpose, according to this invention, the cylinder or the like metallic support previous to being coated with the light sensitive colloidal layer is brought to the same or an adequate temperature as the light sensitive liquid or emulsion itself has during coating. This is attainable in different ways, preferably by dipping the uncoated cylinder or the like in a warmed liquid like water and turning it in the latter until it has assumed the temperature of said liquid, whereupon it may be removed from the liquid and may be coated with the light sensitive colloidal layer, if necessary after previously being dried. Instead of being treated in the aforesaid manner with water or any other liquid, the cylinder or the like may be brought to the desired temperature by other means, for instance by being inserted in an air But the first named type of heating is preferable, because thereby the cylinder may be brought to the desired temperature with greater speedand security.

If it is especially intended to coat a cylinder- .preheated in the aforesaid manner, this may be done for instance by dipping same in a container filled with'the light sensitive fluid or emulsion,

and revolving the cylinder when it is dipped in the liquid. For instance the liquid may be kept in a container and the cylinder is dipped in same from above in horizontal position. To assure perfect uniformity of the coating one may proceed preferably as follows. The container of the light sensitive colloidal liquid, which is open at the top, e. g. an oblong pan, is set in a second corres at t e top and is filled with water or with any any other suitable liquid, in such a manner that the pan filled with the colloidal liquid will 'be' kept floating therein. The second or outer container is fitted with inlets and-outlets for the liquid. By keeping the water of the outer container at an adequate temperature, care may be taken of constantly keeping the colloidal fluid in the central pan at a desired temperature during with water, in such a manner that it does not coating. This is attainable either by heating the outer container externally in an adequate manner, or by continuously passing water or any other liquid of the desired previously adjusted temperature through the outer container.

In order to bring the colloidal fluid of the central pan into contact with the surface of the cylinder or the like for coating same, preferably the following arrangement may be made. The bearings and the driving mechanism for revolving the cylinder to be coated are fixed in a definite invariable position and level above the outer water container. The pan or the like filled with the light sensitive colloidal liquid is now inserted in the outer container, not yet or only partly filled yet come in contact with the cylinder. By filling the outer container with water or the like, the

' pan filled with the light sensitive fluid is gradundingly shaped container which is also open ally raised until the revolving cylinder steeps in. The speed of rotation of the cylinder during its dipping into the light sensitive fluid is selected so that also by this means the uniformity of coating is assured. To reach this aim, as has been found, the speed of rotation must not be high. For each case the suitable velocity must be stated by experiments according to the viscosity of the colloidal solutionf After the cylinder has been revolved a suflicient time in the light sensitive liquidin order to obtain the desired thickness of coating, so much water is drained off from the outer container thatthe pan filled with the light sensitive liquid sinks down sufl'iciently Pto come out of contact with the cylinder.

The dipping of the cylinder to be coated into the light sensitive liquid in thecontainer may, however, also be performed bylowering the cylinder together with its bearings and, if desired, with the driving mechanism, toward the surface of a body of the colloidal coating liquid until the cylinder surface contacts the surface of said body. After coating, the cylinder and liquid may be separated again from one another by raising the former horizontally.

Furthermore, it is possible to have the light sensitive colloidal fluid flowing from aboveonto the cylinder, which is fixed in a horizontal. level and revolves as has been previously described,

pose the cylinder may also be warmed p either from the beginning or afterwards and gradually from the inside. Suitably heating or warming up set in already when' the separation of the cylinder from the colloidal liquid in the container begins, and increasein accordance to the progression of this separation.

i'I'he axis of the revolving cylinder may be arranged horizontally. But it is also possible to arrange it somewhat inclined to the horizontah The latter is of special importance during the separation of the liquid in thecontainer and the cylinder. Not only. when the separation is caused by lifting the cylinder from the liquid of the container, but also when it is effected by withdrawing the liquid from the cylinder, finally liquid and cylinder will touch one another only v in one point or with a narrow sharp edge so that the last part of the separation of fluid and cylinder will happen at a single punctiform spot.

Correspondingly there is no need that the axis of the cylinder retains the aforesaid slope constantly, i. e. during the procedure of the coating itself, but it is suflicient that it has this position only whilst liquid and cylinder are separatedfrom one-another. Thus one can keep the cylinder in a horizontal position during the coating proper and give some slope to its axis only during the separating process.

It depends on the viscosity of the applied colloidal fluid how much the cylinder is to be sloped. Generally it is suflicient to raise the one end of the cylinder for a few centimeters in comparison with the other. Also the revolving speed of the cylinder to be maintained during the treatment proper and during the separation of cylinder and fluid also, essentially depends upon the vis-v cosity'of the applied colloidal fluid. In this case,

also, the fluid and the cylinder may be'separated by any suitable method, e. g. simply by draining ofl gradually the colloidal fluid from the coating vessel or by mechanically lowering the whole coating vessel with the fluid contained therein.

As already stated, it is oi particular importance for the perfectly uniform coating to rotate the cylinder whilst coating exceedingly slowly. When following the method described above, where the cylinder is inclined, a speed of rotation of for instance about 7 revolutions per minute is suitable. But when working after the method when the cylinder is in a horizontal position the speed of rotation must be so slow, that asingle rotation requires several minutes', preferably about 5 minutes. The cylinder .also in this case suitably should be preheated,

preferably to such a degree'that the colloidal fluid dries at once on the cylinder as it revolves therein, so that any draining of! of fluid from the cylinder turning out of the immersion fluid is prevented. Thus a very uniform coating is obtained.

Although the cylinder rotates exceedingly slowly during coating, thenwhole process in the use of this method requires less time as in the method working with the inclined cylinder, be-

cause the separation of the cylinder from the immersion fluid, when the cylinder is inclined.

method savings-of coating fluid may be obtained,

since the cylinder, if kept horizontally, requires only: a very slight steeping into the coating fluid, whereas with the inclined cylinder the depth of the immersion fluid in the coating vessel obviously must be correspondingly larger.

The heating of the cylinder before or during coating may be executed alsoin such 'a manner that a heating medium .is passedthrough same or that it is heated electrically, or the like.

In the drawings some embodiments of devices for coating printing supports are shown, Figures 1 and 2 representing a specially suitable device for coating metal cylinders uniformly with a light sensitive colloidal fluid and Figures 3 to 5 showing devices for. coating metal plates. Fig. 1 shows a vertical section through such a device with the lower part of the cylinder to be coated.

Figure 2 is a view, (partly insection) of the device shown in Fig. l the cylinder I being omitted. Fig. 3 shows an essentially diagrammatical side view of a device for coating plates, partly in section, the cover being opened. Fig. i is a side view of the cover itself and Fig. 5 is a somewhat modified form of execution, of this device in closed position and. in section.

The device illustrated in Figs. 1 and 2 renders possible a uniform coating also during the period when separation of cylinder and coating fluid goes on, so that the coating will be perfectly unifor the fluid, but it is rotated only along the top opening of a container fllled with the fluid in such away, that its surface just is touching the surface of the coating fluid and the fluid is drawn out of the groove-like container by the action of the adhesion of the fluid to the revolving cylinder or of the surface tension of the fluid.

Therefore the separation of cylinder and coat-.- ing fluid can be made very quickly and briefly, so that during such separation no broad uneven streak whatever will be formed on the cylinder. To further restrict this eventually uneven streak of separation on the cylinder, it is suitable to make rather narrow theopening of the coating vessel along. which'the cylinder revolves, said opening-or vessel thus obtaining the shape of a ,narrow groove or channel with at least the same length as has the. cylinder that is to be coated. Suitably the narrowness of the groove is thus proportionated to the diameter of the cylinder, that a dipping oi the latter into the 4 grooveis made impossible and it can just revolve along the surface of the gutter. The breadth of the groove orchannel, if necessary, may also be made adequate to the quality of the coating. fluid, especially to its'viscosity.

Since in this case only a rathennarrow part of the surface of the coating fluid is left free or brim of the channel 2.

and furthermore this part is covered by the cylinder above it, the danger of dust particles accumulating on the surface of the coating fluid is extremely small. But to avoid that dust particlesby air draughts or the like are brought (see Fig. 1) a groove or channel 2 is arranged which is open at the top and extends over the whole length of the cylinder If desired, its top opening may be closed by a cover 3 suitably to be slid over from the front. The bottom part of the channel 2 is connected with a compensating reservoir of conveniently the same horizontal length as the channel 2 (see Fig. 2), communicating tubes 4 being arranged for this purpose. Tubes 6 (Fig. 2) feed the colloidal fluid to the compensating reservoir 5 from a reservoir, not shown. The interior of the compensating reservoir 5, which is suitably closed by a detachable cover 1, is provided with a number of overflow tubings 8, the tops of which are exactly on the same level with the upper opening Adequate feeding of the coating fluid thus provides that the channel 2 will remain permanently filled up to its top.

As may be seen from Fig. l, the top border of the channel 2 is bevelled on either side, as shown at 9 This will prevent any liquid from collecting on these edges and come therefrom in contact with the cylinder, possibly causing rather broad uneven streaks. The said bevels need, however, not reach the inner edges of the channel.

The apparatus consisting of the coating channel 2, the compensating reservoir 5 and the connecting tubes 1 is inserted in a closed case l0 and rests therein exactly horizontally on bases screws l2, by which it may be arranged exactly in a horizontal position by means of a hydraulic or spirit-level, not shown. The case I0 is filled by a feeding tube l3 with a liquid of adequate temperature, for instance with warmed water,

the temperature of which is controlled by a thermostat, not shown. The liquid drains off through the tube l4 (Fig. 1).

In front of the groove 2 leather-wipers I5, l6 are arranged extending also over the whole length of the cylinder. In the embodiment shown in Figs. 1 and 2, these wipers IS, IS are fitted to rods l1, l8 fixed to a joint or hinge l9, which is connected to a'counter weight 20. Instead of the counter weight obviously also springs may be employed.

To the other side of the channel 2, next to the case lo, a wall 2| is arranged suitably extending up to cylinder I, thus forming a lateral closure between the same and the case l0 and acting as a dust-guard. This wall 2| may be fixed to the case I0 by means of thumb screws 22 and may be hinged at 23, thus being detachable by loosening the screws 22.

If desired, the wipers l5, l6 may be replaced by a second wall protecting against dust and cor- The case ID on its side rests on adjusting,

responding to the wall 2| but arranged in front of the-coating channel 2, or such a wall may be arranged alongside the wipers l5, l6.

When using this device, the case I'll is first filled with water or with any other suitable liquid having the desired uniform temperature, and also the compensating reservoir 5 is filled with the coating fluid. The latter passes from reservoir 5 through the tubes 4 to the coating channel 2 and fills it up to its brim, the level of which corresponds to the top of the overflow tubes 8. Till this moment the cover 3 of the coating channel 2 may be kept closed. When the cover is removed, either the cylinder I, which, if desired, may be preheated, is lowered down near to the brim of channel 2 or. the latter is raised together with the case III, e, g. by means of the adjusting screws l2 towards the cylinder until the surface of the fluid of channel 2 comes in contact with the cylinder. If now the cylinder is revolved with convenient slowness, it takes up the coating fluid from the groove 2 in consequence of the adhesion or surface tension of said fluid, and the cylinder is thus coated with perfect regularity, whilst from the not shown reservoir a corresponding quantity of'coating fluid follows into the compensating reservoir 5. When the entire cylinder in this way is coated uniformly with the coating fluid, separation is executed again either by raising the cylinder or by lowering the case H] with the coating channel. As desired, the cylinder obviously may be rotated once or repeatedly along the coating channel. If a quickly drying fluid is used, e. g. such as dries quickly under the action of the heat of the cylinder, the thorough drying happens regularly already before the coated part of the cylinder passes the guard-wall 2|.

The speed of rotation of the cylinder obviously depends on the one hand upon the viscosity of the applied fluid and on the other hand upon the drying speed,'and similar points. Instead of photographic copying solutions any other liquids may be utilized for coating the cylinder, e. g. varnish solutions as used for instance also for photographical purposes, also liquids of any other quality. As may be easily seen, the device permits the coating of cylinders with any diameter whatever, without any important changes being needed for this purpose. Also shorter cyl inders than such the length of which corresponds to the length of the coating groove may obviously be treated on the'apparatus.

Special stress must be laid, when plates and metal cylinders are coated for photographical purposes, to attain a perfectly dustless coat, as

already indicated above, For this purpose, the

case of the cylinder to be coated or the case of a into contact with the cylinder or plate to be coated. v

If desired, two or more/centrifuges or cylinders can also be arranged jointly in such a closed case.

- To be safe, the pressing or suckingof pure or purified air when using the apparatus must set in before the coating begins. If desired, the purified air entering the case may previously be ed as, a whole, e. g. by means of aheating jacket indicated purpose when coating photographic plates are shown in Figs. 3 to 5. The centrifuge box or case a is hermetically closed at all sides and preferably has a rounded shape. Its cover b preferably is manufactured rather weighty, and

v the rim of this cover is bent upwards like a collar (see Figure 4) Beneath this rim a packing ring 0 of rubber or the like is fastened, so that the cover will close the case a firmly and impermeably to dust. It is-of importance that the inner surfaces of the case a. as well as of the cover b are perfectly smooth, as may be reached without difliculty by using materials such as an artificial resinous'mass, aluminium or any other rustproof,

metal, metal alloys or the like.

At the smooth lower side or cover .b heating tubes d are fitted, preferably in a segmental arrangement to one another, as shown in Figure 3, all parts of the plate e to be coated thus being warmed uniformly, Preferably these heating tubes are closed on all sides and have also av perfectly smooth surface. Instead of such heating tubes, heating boxes ,or heating plates which may be heated electrically, and the like, may also be provided for, and, generally speaking, the

heating may be performed in any suitable way. It always remains of high importance, that no particles of dust or dirt at all enter the case also through the heating device, and that this device is arranged in such a manner that the accumulation of particles of dust or dirt on this device is prevented. 4 v

The'base f for the plate e to erably also consists of a material with perfectly smooth surface such as artificial resin, polished aluminium, or the like, and, to eliminate disturbing air eddies, may be of a smooth, dishlike shape. It should not be larger than the plate to be coated in order to avoid that at the rim old crusts of coating fluid may adhere. If very large plates are to be coated, for which the base 1 is too small, first a larger, rather thin, firm and clean plate a, e. g. a steel plate can be laid on the base ,1, whereby an even supporting surface of sufficient dimensions is obtained for the plate e to be coated. If neces-- sary, the plate 9 may be specially'fastened to the base I. The dimensions of the base I in proportion to the periphery of the centrifuge case a are preferably such as to assure for the edge 71. of the base i a suflicient distance from the inner side wallor face i of the centrifuge case a. Thus it will be attained that no coating fiuid is thrown against said inner face i, where it could form deposits and crusts. To obtain this same purpose preferably the centrifugal speed should not be' too large.

A shaft '11 passes through the bottom of the centrifuge case a, a special packing, not shown in the drawings, being provided for preventinl dust' particles or the like from entering the we at this spot. Several washers, the one above thg other, or a gland may be arranged for this pur' pose, as the usual ball bearing will not be sufficient. The bottom of the centrifuge case a is filled with water or any other suitable liquid k. This liquid serves on the one hand to receive and I fix any particles of dust and dirt which might enter thecase, and on the other hand to take up the coating fluid thrown off from the plate 2, asshownby thedotted arrowheaded lines in In the outer wall 7' of the centrifuge case a an airduct I opens, by means of which filtered ,air is pressed from a container m into the centrifuge case a. As filtering mass for instance the so-called Raschig-rings wetted by oil or the like may be used,.said rings being arranged in a funnel n. In a proper way, e. g. by means of an oil separatoro, care is taken to. prevent that oil is carried from the filter mass into the centrifuge case a. The air may, however, also be purifiedby pressing it through a water tank. In the interior of the centrifuge case a above he orifice of the tube 1 a guide plate p is fixed in such a manner that the formation of air eddies in the interior .of the case is avoided as much. as possible, and that the air moves along the inner wall of the centrifuge case in middle height.

Small openings-not shown in the drawingsare provided at convenient places of the centrifuge case a, to allow the air pressed or sucked in to escape. Any particles of dust and dirt, which at the beginning may yet be in the case, are taken with said air if they are raised up by it. On the other hand the entering of dust particles from without through the aforesaid openings isprevente'd by said evading pressed be coated prefair. I If desired, however, these outlet openings may be provided with non-return valves, admitting only the discharge of the air but not-its entering through these openings.

To be quite safe, the centrifuge case before the coating of the plates is specially cleaned, first my rinsing with filtered waterand then by blowing filtered air through it. The filtered water may be introduced through one or more holes or small tubes, not shown, which may be arranged in the cover b of the case and if necessary may be closed. Through the same tubes or openings the coating fluid may also be introduced.

The plates are coated in this device preferably in such a manner that, when the plate is laid in, first the cover b is closed and the case a is cleaned by blowing through filtered air. Then filtered water is introduced to wash out any dust anddirt particles still present, whereaiter the coating fluid is applied to the plate through the small tubes q or the like, which are arranged in the cover and can be closed when not in use. i

The variation of the centrifuge shown in Fig. 5, differs from that represented in Figs. 3 and 4 essentially in that the air is pressed or sucked in through the water arranged on the bottom of the centrifuge, in order to assure the freedom of said air from dust before it passes the free room of the centrifug case. For this purpose. preferably such an arrangement is provided for, that the air by .means ofa tube fitted to the bottom is. conducted under a cap arranged above the water level, the side rims of said cap extending below the water surface, so that the air can enter the free interior of the case only after having passed through aid water. Thus the air is freed even from the finest dust particles possibly car- I ried by it before.

According to this embodiment, a tubing 3 serving to blow in air is introduced through the botfastened at a pierced structure at fitted to the bottom-t of the case a. The air entering the room beneath the cap 11 through the tube s from below in the direction of the arrows is pressed from there through the water In and reaches the free interior of the case a passing the interstices or holes to of the structure u. When thus passing through the water It, the air is perfectly freed from any dust. The discharge of the pressed in air from the casing also in this case can be effected by means of openings, conveniently arranged in the cover b of the casing and fitted with non-return-valves.

The tube for introducing the'air with the cap belonging thereto may be arranged at any other place of the bottom of the case, and the cap 12 may be fastened otherwise than by the pierced structure a, e. g. by means of bars or bows joined to the end of tube a and holding the cap with some distance over it.

The device for passing the air through the water can also simply consist of a tube twice or repeatedly bent in serpentines reaching over the water level but terminating beneath said level, the cap 1: then being unnecessary.

Having now particularly described and ascertained the nature of my said invention, I declare that what I claim is:

Process for uniformly coating the peripheral surface of a metal cylinder with a layer of a light-sensitive colloidal fluid coating composition for the photomechanical production of a printing form, which comprises maintaining a body of said fluid composition and the cylinder at substantially the same elevated temperature while practicing the succession of steps consisting in immersing a portion of the peripheral surface and draining back of fluid composition over succeeding portions of emerging surface is prevented.

ROBERT KAULEN. 

